Lock-stitch sewing-machine



H. CORRALL.

LOCK STITCH SEWING MACHINE.

APPLICATION FILED JUNE 13. I918.

Patented Dec. 13, 1921.

2 SHEETSSHEET 1.

9% A TORNEY WITNESSES H. CORRALL.

LOCK STITCH SEWING MACHINE.

APPLICATION FILED JUNE 13. [9H3- Patented Deo. 13, 1921.

2 SHEETS-SHEET 2.

INVENTOR M M, 5%

a1 zT ifizY Ck m UNITED STATES HERBERT COR/BALL, 0F HELENSBURGH, SCOTLAND, ASSIGNOR TO THE SINGER M FACTURING COMPANY, A. CORPORATION OF NEW JERSEY.

PATENT OFFICE.

ANU-

Application filed June 13,

To all whom it may concern:

Be it known that I, HERBERT'CORRALL, a subject of the King of the United Kingdom of Great Britain and Ireland, and residing at Oakfield, Helensburgh, Dumbartonshire, Scotland, have invented certain new and useful Improvements in Lock-Stitch Sewing- Machines, of which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates to improvements in rotary hook lock-stitch sewing machines and has for its primary object to provide a construction of lower thread-handling mechanism which will increase the capacity of such machines, which is simple and inexpensive to manufacture and of which the entire thread case can be readily removed and replaced and any necessary adjustments effected by an unskilled operator.

A further object of the invention is to provide a rotary hook mechanism which will not become clogged with lint or thread ends.

Still further, the invention has for an object the provision of rotary hook mechanism which will closel control the needle-loop and prevent twistlng or kinking of the loop as it is being drawn up after having been passed about the thread-case.

Further objects of the invention will appear from the following description and appended claims.

The invention, in its preferred embodiment, comprises a cup-shaped loop-taker, the rim of which is cut away to form a loopseizing beak and a loop-arresting heel having an inclined face. The loop-taker has an inwardly directed ledge forming an open raceway for the reception of an outwardlv projecting rib formed on a thread-case having an axial pin upon which the bobbin is j ournaled. The thread-case is formed with a pair of spaced holding lugs which loosely embrace acomplemental rotation-restraining lug fixed to the machine 'bed. The bobbinthread is led under a fiat tension spring mounted on the face of the bobbin-case. From the tension spring the bobbin-thread passes upwardly through an aperture in one of the holding lugs and is thereby closely guarded and prevented from being caught by the loop-taker beak. The peripheral edge of the bobbin-case rib is not circular but is constituted by two semi-circles of equal radii, the center of the upper semi-circle be- Specification of Letters Patent.

Patented Dec. 13, 1921.

1918. Serial 110.239,?35.

ing approximately coincident with the axis of the hook and bobbin-supporting post whlle the center of the lower semi-circle is displaced slightly above the axis of the bobbin-supporting post. As a result the thread-case is permitted some freedom of movement vertically to take care of broken thread ends and to insure that the raceway be kept clear.

The thread-case is formed adjacent the holding lug on the cast-off side with an inclined edge or face conforming to the inclined face of the loop-arresting heel of the rotary hook-member. During the rotation of the hook, a narrow gap directed toward the stitching point is therefore presented at the proper time to permit the escape of the needle-loop and prevent twisting or kinking of the latter as itis being drawn up beyond the range of the loop-seizing beak. A light helical spring bears sidewise against the front of the bobbin-case to lightly detain the latter in its raceway and permit passage of needle-loops about the bobbin-case at high speed.

The invention is designed more particularly to be embodied in machines of the type in which the hook performs a plurality of rotations for each reciprocation of the needle.

In the accompanying drawings, Figure l is a plan and Fig. 2 an end view of the hookshell detached. Fig. 3 is a plan and Fig. 4 a rear end view of the bobbin-case. is an end view and Fig. 6 a side elevation partly in section showing assembled the hook, bobbin-case and bobbin-case retaining device. Figs. 7 8 and 9 are perspective views showing the bobbin-case stop-member, the bobbin-case and the hook-shell. Figs. 10 and 11 are perspective views, showing respectively, the hook-shell and the bobbin-case y from behind. Fig. 12 is a vertical crosssection through the assembled hook-shell and bobbin-case. Fig. 13 is a side elevation of the bobbin-case showing the tension spring. Fig. ll is an end View of the assembled mechanism showing the hook in cast-off posi tion. Fig. 15 is a perspective View showing the loop escaping through the narrow gap between one of the holding lugs on the bobbin-case and the heel of the loop-taker, and Fig. 16 is a perspective view of the bobbin-retaining and ejecting lever.

In the preferred embodiment of the inven- Fig. 5

tion, as illustrated, 1 denotes the cup-shaped hook-body of which the rim is formed with an inwardly extending annular ledge presenting an open-sided raceway affording a bearing for the peripheral rlb 3 on the bobbin-case 4, which latter is held 11]. position by a retaining device hereinafter referred to and also by engagement of holding lugs 5, 6 thereon with a coacting lug 7 on a stationary stop-member 8, whereby the bobbin-case is restrained against rotation. The space hetween the lugs 5 and 6 is enough greater than the thickness of the lug 7 to permit escape of the needle-loops.

Between the loop-seizing point of the beak 9 and the heel 10 is a gap of substantial magnitude bridged by a guard member 11 and subtending at the center of rotation of the hook on the particular embodiment of the invention illustrated an angle of approximately 45 degrees.

The loop-seizing point of the beak 9 is located substantially in front of the internal bearing ledge 2; and overlying the beak 9 is a spur-like thread-guard 12 forming with the beak 9 a throat 12 which receives the needle-loop and spreads the latter for passag about the thread-case. The heel 10 is cut away to present an end face inclined rearwardly relatively to the direction of rotation, the an le of inclination being preferably substantlally 45 degrees.

As shown in Fig. 4, the peripheral edge of the rib 3 is constituted by two semi-circles of equal radii but difierent centers, the center for the upper semi-circular portion of the rib 3 is located at 0 approximately coincident with the axis of the supporting post 13' for the bobbin 13. The center for the lower semi-circular portion of the rib 3 is located at the point 0 which is spaced slightly above the center 0'. Thus, a certain amount of vertical play is provided between the bobbin-case and hook-member and the clearance afforded is sufiicient to permit escape of any broken ends of thread without risk of -jamming while the maximum surface of bearing contact between the rib and the raceway is insured.

he rib 3 is cut away to present two appositely inclined edges 14, 15 merging into the edges of the holding lugs 5, 6, the inclination of th edge 15 on the cast off side being in substantial conformity with or somewhat greater than that of the edge of the heel so that, in the rotation of the hook, there is presented at the proper time and in the immediate vicinity of the holding lug 6 on th cast-off side a narrow gap, Fig. 15, for escape of the needle-thread loop which has been carried around the bobbin-case 4 and has been under perfect control until the said narrow gap is opened for its passage.

The bobbin-case 4: comprlses a unitary part of substantially disk form of which the forward face is fitted with a blade tensionspring 16 adjustable as by manipulation of the screw 17, the free end of the tension spring 16 being located adjacent to a threadguiding passage or duct which traverses the holding lug 5 on the loop-seizing side of the bobbin-case.

The bobbin-case is retained against the ledge 2 of the raceway by means of a light helical spring 18 having one or more convolutions bearing on the lower portion of the front of the bobbin-case 4, such spring 18 beinrr fitted in a recess in one arm 19 of a lever which is normally held in position by a manually controllable latch 20 and of which the other arm 21 is movable into engagement with the rear of the bobbin-case and may thus serve as an ejector. The lever 19, 21 is pivoted at 22 to the bracket 23 screwed to the bearing lug 24 depending from the bed of the machine. The latch 20 is pivoted at its upper end to the lever-arm 19 by means of the screw 25 and at its lower end is formed with an inclined end-face 26 which snaps into position over the similarly inclined face 27 of the projection 28 of the bracket 23, thereby wedging the arm 21 tightly against the upper face 29 of the bracket 23 and locln'ng the lever 19, 21 in closed position.

The latch 20 is urged outwardly by means of the spring 30 one end of which is seated within the slot 31 in the latch and the other end of which bears against the bottom wall 32 of the cut in which the latch is mounted. When the latch 20 is pressed inwardly, the lever 19, 21 may be rocked to remove the spring 18 from in front of the bobbin-case and to cause the arm 21 to strike and eject the bobbin-case. When the lever 19, 21 is in closed position the retaining spring 18 serves to lightly check the limb of the needle-thread loop at the front of the bobbin-case after it has passed about one-half way around the bobbin-case so that any slack in the needle-thread loop is taken up and there is no risk of the rearward limb of the loop lagging behind and failing to clear the bobbin-case. The spring 18 bears lightly against the thread-case and permits passage of the needle-loops at high speed.

The machine 1s equipped with the usual reciprocating needle 33, throat-plate 34 and four-motion feed-dog 35 coiiperating with the resser-foot 36. As the needle descends preparatory to throwing out its loop the feed-dog descends at the end of its feeding stroke. As the needle rises. the loop is seized and drawn out to cast off position. Fig. 14,- by the loop-taker. When the loop-taker reaches cast-off position the feed-dog rises to begin its feeding stroke, and as the work is fed, the pull on the bobbin-thread holds the thread-case in contact with the upper portion of its'raceway, at the same time turning the thread-case slightly to draw the lug 5 in contact with the lug 7 and thereby space the lug 6 from the lug 7. The usual take-up, not shown, rapidly draws up the needle-loop and at the instant the inclined heel 10 passes the inclined face 15 a narrow gap is afforded, Fig. 15 which is inclined toward the stitching point and permits the escape of the needle-loop while guiding the latter toward the stitching point and reventing its twisting or kinking until it as been drawn up beyond the range of the loop-seizing beak 9. As the inclined heel is devoid of spurs or projections and is spaced a substantial distance in advance of the beak 9, a material time interval is afforded for the drawing up of the needle-loop above the path of the beak 9 before the latter reaches the needle-hole at the completion of its loop-seizing rotation, whereby the possibility of second looping or the catchingof the needle-loop by the loop-seizing beak on its idle rotation is avoided.

While the invention is herein shown as adapted to a machine in which the hook rotates around a horizontal axis it will be obvious that it is also applicable to a machine in which the hook rotates around a vertical axis. In the latter instance the bobbin-case may be held in position by the action of gravity.

The various features of novelty of the device shown and described are of my invention.

Having thus set forth the nature of the invention, what I claim herein is 1. In a lock-stitch sewing machine, in combination, a reciprocating needle, a rotary hook adapted to make a plurality of rotations for each reciprocation of the needle and formed with an open-sided raceway, said rotary hook being further formed with a loop-seizing beak and with a loop-arresting heel spaced circumferentially from and a substantial distance in advance of said beak, said rotary hook being shaped to permit the escape and drawing up of the needle loop above the path of said beak before the latter reaches the needle-hole at the completion of its first or loop-seizing rotation, and a bobbin-case restrained against rotation within the field of action of said rotary hook.

2. In a lock-stitch sewing machine, 1n combination, a reciprocating needle, a rotary hook member having a loop-seizing beak and a loop-arresting heel presenting a face inclined to the path of movement of said beak, a stationary thread-case embraced by said hook member and formed with a bearing rib which is cut away to present on the cast ofi side an end face inclined similarly to the face of said heel, whereby, at one point during the rotation of the hook a narrow gap inclined toward the stitching point is presented to uide and closely control the escaping nee le-loop.

3. In a sewing machine, in combination, a rotary hook formed with an internal ledge presenting an open raceway, and a bobbincase restrained against rotation and formed with a peripheral rib in bearing engagement with the raceway, the peripheral edge of said rib being constituted by two semi-circles of equal radii but different centers, substantially as and for the purpose specified.

4. In a lock-stitch sewing machine, in combination a rotary hookformed with an internal ledge presenting an open raceway, and a bobbin-case formed as a unitary part of disk form having a peripheral rib in bearing engagement with the raceway, said bobbincase being formed with holding lugs one of which is traversed by a bobbin-thread passage, and a bobbin-thread tension leaf-spring secured to the forward face of the peripheral rib of said bobbin-case adjacent said thread-passage.

5. In a lock-stitch sewing machine, in co bination, a rotary hook formed with an open raceway, a bobbln-case accommodated therein and restrained against rotation, and a bobbin-case retaining device including a helical spring having one or more convolutions bearing on the front of the bobbin-case, as and for the purpose specified.

6. In a lock-stitch sewing machine, in combination, a rotary hook formed with an open raceway, a bobbin-case accommodated therein and restrained against rotation, and a bobbin-case retaining device including a helical spring one end of which bears sidewise against the front of said bobbin-case.

7 In a sewing machine, in combination, a circularly moving loop-taker, a bobbin-case embraced within the path of movement of said loop-taker, a bobbin-case ejecting lever adapted to strike one face of the bobbin-case when swung to ejecting position, and a bobbin-case retaining spring carried by said lever and bearing upon the opposite face of the bobbin-case when in running position.

8. In a sewing machine, in combination, a rotary hook member formed with an open raceway, a bobbin-case fitted to said raceway and restrained against rotation, an ejectorlever having arms disposed respectively in front and in rear of said thread-case, and a retaining spring mounted on said lever and bearing lightly against the front face of said thread-case.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

HERBERT CORRALL.

Witnesses:

- VVALLAGE CRANSTON F AIRWEATHER,

HENRY MASON. 

